Fluid-solid propulsion unit and method of producing gaseous propellant



June 9, 1964 W. H. AVERY 3,136,119

FLUID-SOLID PROPULSION UNIT AND METHOD OF f PRODUCING GASEOUS PROPELLANT2 sheets-sneu 1 Filed Sept. l2, 1952 I j INVENTOR ML MM H. l/Ef/ATTORNEY United States Patent 3,136,119 FLUID-SOLID PRQPULSION UNIT ANDMETHOD F PRODUCING GASEGUS PROPELLANT William H. Avery, Silver Spring,Md., assignor to Research Corporation, New York, NX., a corporation ofNew York Filed Sept. 12, 1952, Ser. No. 309,239 16 Claims. (Cl.Gil-35.4)

This invention relates to a rocket propulsion system and particularly toa rocket propulsion system utilizing a liquid fuel and a solid oxidizer.

Rocket propulsion systems are finding extensive application asassist-take-off devices, boosters for missiles, and projectiles. Theseveral systems previously used may be classified into two basic typesin accordance with the physical state of the fuel and oxidizer employed,i.e., liquid propellant or solid propellant. A third type, a gaseoussystem, is obviously undesirable from the standpoint of the very largespace requirements in order to provide an adequate fuel supply.

The liquid propellant systems have advantages in controllability, lowcost, and high performance, but all liquid oxidizing agents presentsevere storage and handling problems. For example, some liquidoxidizers, such as HNO3 H2O2 are corrosive, unstable and toxic whileothers, such as N204, are toxic and volatile and others, such as aliquid O2, require insulation and refrigeration. In addition,conventional liquid systems require complex feed mechanisms and precisecontrol to eliminate the hazard of explosion. The solid propellantsystems are simpler and may be more reliable than the liquid propellantsystems, but they are explosive, non-controllable and expensive.

Several systems employing fuels and oxidants, respectively in differentphysical states, had been developed.

' One such system comprised the reaction of aluminum powder suspended ina liquid hydrocarbon with liquid oxygen and involved the attendantdisadvantages of the liquid type systems outlined above. Another systemproposed the use of liquid nitrous oxide for burning solid carbon andstill another system proposed the burning of a solid plastic, e.g.,polythene fuel, with a liquid oxidizer, e.g., hydrogen peroxide. Thelatter two systems also involved the problem of storing and handling ahighly corrosive, unstable, or toxic liquid.

Solid oxidizers were developed to provide auxiliarycombustion-supporting agents for fuel-rich solid propellants. Theseoxidizers were included in a rocket chamber containing a solid fuel,eg., nitroglycerine or nitrocellulose, for supplying additional oxygento promote complete combustion of the solid fuel and thereby increasethe combustion efficiency. This was essentially a solid type system andembraced the disadvantageous features of non-controllability,expensiveness and short duration operation.

In the light of the foregoing review of previous rocket propulsionsystems and of their attendant shortcomings, the present inventionembraces, as an object, the provision of a rocket propulsion unit whichcombines the beneficial features of both the liquid and solid typesystems but excludes the undesirable features of each.

Another object of the present invention is to provide a rocketpropulsion unit that is inexpensive, simple but reliable, safe andcontrollable.

A further object of this invention is to provide a rocket propulsionunit embodying the above outlined features and lemploying a liquid fueland a solid oxidizer.

Further objects and attendant advantages of this invention will becomeevident from the following detailed description when read in conjunctionwith the accompanying drawings, in which:

FIG. 1 is an axial section of a propulsion unit embodying the presentinvention;

FIG. 2 is a sectional view on line 2-2 of FIG. 1;

FIG. 3 is a fragmentary axial section illustrating a modification of theignition system shown in FIG. 1;

FIG. 4 is a sectional view on line 4-4 of FIG. 3;

FIG. 5 is a fragmentary axial section illustrating a second modificationof the ignition system shown in FIG. 1;

FIG. 6 is a sectional View on line 6-6 of FIG. 5;

FIG. 7 is an axial section illustrating a modification of the propulsionunit shown in FIG. 1;

FIG. 8 is a diagrammatic view showing the electric wiring of theignition system employed by the unit shown in FIG. 7; and

FIG. 9 is an axial section illustrating a second modification of thepropulsion unit.

Referring now to FIGS. 1 and 2, there is shown a rocket propulsion unitembodying the present invention and including, in general, a fuelinjection system 11, an ignition system 12, a combustion chamber 13, anexhause nozzle 14, and a streamlined cowling 15 enclosing theseelements.

The combustion chamber 13 is comprised of a hollow cylindrical casing16, having flanges 17 and 18, on the fore and aft ends, respectively,thereof, and contains a hollow cylindrical grain of solid oxidizingmaterial 19, which will be described more fully hereinafter. The foreend of the nozzle 14 is formed with a fiange 21 which is secured, as bybolts 22 and nuts 23, to the flange 18 on the aft end of the cylindricalcasing 16. The aft end portion of the nozzle 14 is shaped to present astreamlined outer surface 24 and is formed with an annular recess 25 forreceiving the aft end of the Cowling 15.

A head cap 26 of cup-like construction having an end wall 27 and acylindrical side wall 28 withav flange 29 at its open end, is positionedat the fore end of the cylindrical casing 16 with said fiange fastened,as by nuts and bolts 31, to the flange 17 on said casing. The end wall27 of the head cap 26 is formed with a central opening 32 for receivinga fuel injection nozzle 33, to be described later in connection with thefuel injection system 11, and a pair of orifices 34, one on each side ofsaid opening, for receiving a pair of air or oxygen injectors 35. Theside wall 28 of the head cap has formed therein an kopening 36 whichreceives a spark plug 37 or other sparking means. For optimum ignitionperformance,

it is preferable to direct the orifices 34 and consequently the air oroxygen injectors 35 in such a manner that the gas emitting therefromwill impinge upon the grain 19 in the combustion chamber 13.

The fuel injection system 11 includes a fuel tank 38 which is connectedby a conduit 39 to the fuel injector 33 and a suitable control valve 41which is positioned in said conduit to permit theregulation ,offuelinjection into the head cap 26. If desired fuel may be supplied froma suitable source other than a separate tank, i.e., the fuel tank 38,specifically provided therefor. If the unit is to be employed as anassist-take-off device for an airplane, or as a booster for a ramjetmissile, fuel may be supplied from the main fuel source of the airplaneor missile.

The ignition system 12 comprises a tank 42, containing compressed air oroxygen, a conduit 43 leading from said tank to the injectors 35, and acontrol valve 44 in said conduit for regulating the rate of injection ofair or oxygen, as the case may be, .into the combustion chamber 13. Thesparkplug 37 is connected to a sourcev tion upon the invention.

Y 3 a anged ring 45 and similarly, attachedby the nuts and bolts 31 tothe ange 29 on the head cap 26 Vis a second tlanged ring 46, both ofsaid rings providing for the support Vof the streamlined cowling on theassembled propulsion unit.

The fuel utilized by this invention may be any one of the numerousorganic or inorganic fuels available; examples of organic .fuels are thehydrocarbons such as kerosene, gasoline and diesel oils. Other organicfuels, which may be used include the alcohols, ketones, ethers, organiccompounds containing sulfur such as Typical thiophene, and organiccompounds containing nitrogen i such as pyrrol and pyridine. Typicalinorganic fuels are the hydrogen-nitrogen compounds, for example am!monia" andA hydrazine. Although specific .fuels are enumerated, it isnot intended to limit the invention to a propulsion unit utilizing thosespecific fuels. Any

fuel of the common variety is suitable for use in this injected. Tominimize storage hazards it is preferable and'possible touse solidoxidizers that are nonexplosive, non-toxic and. non-inflammable.Examples ofV appro priate oxidants are potassium perchlorate [KC104],

ammonia perchlorate [NH4C104], ammonia nitrate [NHQNOSL nitroparalin s,such as hexanitroethane [C2(N02)6] and higher homologues, nitrosylperchlorate V[N0Cl04], nitroxyl perchlorate [N02Cl04], persulfuricacids, such as mono-persulfuric acid [H2805] and disulfurie acid[H2S0S], sodium peroxide [Na202], potassium peroxide [K202], potassiumsuperoxide [K02], sulcompressionlat elevated temperature, a binderfofoxidizing or inert material in the form of a low-melting eutectic fmixture, may be used. Ars' an example, a portion of the oxidant and alow melting nitrate or nitrite, eig., sodium nitrate,V lpotassiumnitrate vor sodium nitrite, would be suitable. The-following is ageneric example of a suit# able composition. Although specificproportions of the ingredients are set forth, it isfto be understoodthatthese are only typical, and should not be construed as a limita` 1gov 0f the numerous compositions suitable for use in'manuvfacturing theoxidizing grain, the following examples areV presented as illustrativeof compositions having exceptional combustion-supportingcharacteristics. I

CatalystzwManganese dioxide 2 Binder: Eutectic mixture of potassiumperchlorate Percent Y 2 4 v Example Il Oxidant: Potassium perchlorate83' Catalyst: Manganesey dioxide i 2 Binder: Eutectic mixture of sodiumnitrite and potaslsiurn nitrate l5 Y v Example III Oxidant: 'f y yPotassium perchlorate "14 Ammonium perchlorate 56 Catalyst: y

Ferrie oxide and manganese dioxide 2 Oxidant and binder: ammoniumnitrate 28 Y Y 100 Example 17V f Oxidant: 2 f,

Potassium perchlorate 3 3 Ammonium perchlorate y 33 Catalyst: Manganesedioxide and ferricroxide y 2 Oxidantand binder: Ammonium nitrate i 32100*y Example V Oxidantzv Potassium perchlorate V49.4 Ammonium nitrateCatalyst:` v 2 l f. Manganese dioxide Y Ammonium dichromate .6j 2 Y.100.0 In Example I, the` eutectic mixture of potassium perchlorate andsodium nitrate and, `in Example II, the eutec' Examples III', VIV and-Vammonium nitratefitself serves as a binding material as Wellasanoxidant.v ltshouldV be further pointed Vout that in Example V manganesedi- 'Y oxide catalyzes the decomposition of the potassium perchlorate,and ammonium dichroinate catalyzes the de- Example 0 v i l Y PercentOxidant e-.. 83 Catalyst 2 Binder Y l5 and sodium nitrate l5 i lcomposition of the ammoniumv nitrate.y l. The proportions ofoxidant,rca`t'alyst and binder in each` composition mayVA be varied asdesired to produce a large variety ofreifective compositions. Y

The method of fabrication of the oxidizing grains willy depend .upon themeltingV point anddecomposition tem?- Y Vperatu're of the oxidant to beemployed. If the de composi-. f "tion temperature of the oxidant, withthe catalyst added, is

higher than its melting point, afsimplecasting-methodrmay beused.Howevenif the decomposition,temperature is Y .lower than the meltingpoint, then a simple casting method -1 is notsuitable sincedecomposition'willoccur during the casting operation. In-the lattercase, compression`mold ing with a binder at .temperatures'belowy theVmelting point 2 maybe used for consolidating the oxidant into an`oxidizing b grain; ,v Y. Y

'In'operation,. the, control valves 41 andY 44l are `opened to permitvthe injection offffuel and oxygen intothe head 1 cap 26, and thus form acombustible mixture. v A sparkV K vfrom-the spark plug l37 initiates theburning ofthe mixture which then isapplied to thesurface of the grain19. The intense heat produced by the burning mixture causes thev grain19 tok decompose thereby evolving oxygenwhich reacts with more fuel 'toifurther intensify the .heat freleased; The -rate of oxygen evolutionfromthe surfacei ofthefgrain'increasesuntil itis suicient to'burnV the:fuel

being injectedinto the combustion chamber 13 land mainj l tain a sourceof heat adequate to promote further decom 'A position of the grain. Whenthe rate of oxygen evolution is great enough to produce sufficient heatby reaction with the fuel to vsustain the decompositionvrof ,the grain19', the

control valve 44Iis closed thusrshuttingoi Vthe/oxygen.Vv

supply. Concurrently, the production of combustion gases increasesthereby raising the gas temperature and pressure within the combustionchamber 13. The gaseous combustion products discharge through theexhaust nozzle 14 with high velocity and momentum to produce a' forwardthrust. If desired, the fuel control valve 41 may be adjusted to admitmore or less fuel into the combustion chamber. Thus, the forward thrustof the propulsion unit may be regulated.

Combustion within the chamber may be extinguished by turning ofi thefuel control valve 41, when it is desired to discontinue operation ofthe unit. Subsequently, if need be, combustion may be reinitiated byagain injecting fuel and air or oxygen into the head cap 26, andigniting the resulting combustible mixture. The oxygen is then shut offwhen the rate of oxygen evolution from the grain 19 becomes sufficientto support the combustion of the fuel and maintain thetemperature'required for decomposition. It, thus, can be seen thatpropulsion unit of thisl invention can be controlled to produce aforward thrust, or not, as desired.

In the propulsion system shown in FIGS. l and 2, it is preferable toinject air into the head cap 26 at an angle rom the end wall 27, inorder to impinge the burning ignition gases directly upon the grain 19.Nevertheless,

Y several other methods of injecting air or oxygen are possible. Ofthese several methods two are illustrated: one in FIGS. 3 and 4, and theother in FIGS. 5 and 6.

Referring to FIGS. 3 and 4, an orifice 47 for receiving an air injector48, is provided in the side wall 28 of the head cap 26 and is directedtangentially, as shown, into said head cap. In this manner the burningignition gases are given a vortex motion which results in better mixingand complete combustion of the ignition mixture.

In the method shown in FIGS. and 6, orifices 49 for receiving injectors51 are also formed in the side wall 28 of the head cap 26 but aredirected radially, as shown, into said head cap. This modification,although not as effective in heating the grain 19 as those shown in thepreceding figures, is entirely suitable for ignition purposes.

Other means for bringing the grain 19 to its decomposition temperatureare possible. Two modifications of the ignition system are shown inFIGS. 7 and 8, and FIG. 9.

` The modification shown in FIGS. 7 and 8 employs the combustion chamber`13, the exhaust nozzle 14, and the streamlined cowling which weredescribed in connection with the propulsion unit shown in FIG. l, andwhich will not be described further here.

The head cap 52, however, is of slightly different construction andincludes an end wall 53 having a central opening 54 and a pair oforifices 55, one on each side of said opening and a cylindrical sidewall 56.' The central opening 54 receives a fiare tube S7, to bedescribed hereinafter, and the orifices 55 receive a pair of fuelinjectors 58.

As a part of the ignition system 12, the fiare tube 57 is constructedwith a closed end 59 and an open end 61, and houses four flares 62separated from each other by insulating partitions 63, as shown in FIG.8. The flares 62.- are each provided with squibs 64 connected in seriesto a battery 65 and separate poles of a multi-throw switch 66, so thatupon successive actuations of said switch the Asquibs will be detonatedin the order of their proximity to the open end 61 of the flare tube 57.

The fuel injection system 11 is essentially the same as Athat shown inFIG. 1, including a fuel tank 67, a pair of conduits 68 connecting thefuel injectors 58 to said fuel tank and a fuel control valve 69 forregulating the rate of fuel injection into the combustion chamber 13.

The operation of the above described propulsion unit is as follows. Theswitch 66 is actuated to detonate the first squib 64 in the flare tube57. The squib in turn ignites the first fiare 62 which produces anintense heat. The surface of the grain 19 is thus heated to itsdecomposition temperature, whereupon oxygen is evolved. Then the controlvalve 69 is opened to permit the injection of fuel 6 into the combustionchamber where it reacts with the evolved oxygen to further intensify theheat within the chamber. When the flare 62 burns out, combustion of thefuel in the chamber 13 releases sufficient heat to sustain the evolutionof oxygen from the surface of the grain 19 and the temperature andpressure within the chamber build up. The high temperature, highpressure combustion gases produced by the combustion of the fueldischarge with a high velocity and momentum through the exhaust nozzle14 to impart a forward thrust to the unit. If desired the control valve69 may be adjusted to admit more or less fuel into the combustionchamber, thus regulating the magnitude of forward thrust.

Combustion within the chamber 13 may be extinguished by turning off thefuel control valve 69, when it is desired to discontinue the operationof the unit. Subsequently, if need be, the combustion may be reinitiatedby actuating the switch 65 to ignite the second fiare tube 57. Asdescribed'above, the burning fiare heats the surface of the grain 19 toits decomposition temperature and oxygen is evolved. Then the fuelcontrol valve 69 is turned on and combustion proceeds, as previously, toproduce high temperature, high pressure gaseous products which dischargethrough the exhaust nozzle 14 to impart a forward thrust to the unit.Operation of the unit may be discontinued and reinitated as many timesas the number of fiares 62 present in the flare tube 57 will permit.

Referring now to the modification shown in FIG. 9, there is illustrateda propulsion unit comprising the combustion chamber 13, the exhaustnozzle 14 and the streamlined cowling 15 as described in connection withthe FIG. l embodiment. The fuel injection system 11, however, isslightly modified and the ignition system 12 involves the utilization ofa high resistance wire 71 lfor heating the grain 19.

In detail, the head cap 72 is constructed with acylindrical side wall 73and an end wall 74. The end wall 74 has formed therein a central opening75 for receiving a fuel injector 76 and a pair of orifices 77 disposedon either side of said central opening for receiving two insulatingsleeves 78, which support the high resistance wire 71 of the ignitionsystem 12.

The fuel injector 76 is connected by a conduit 79 to a suitable fueltank 81 as in the FIG. l embodiment, and a fuel control valve 82 in saidconduit permits the regulation of fuel injection into the combustionchamber 13.

The ignition system'12 of this modification includes the high resistancewire 71 which extends into the combustion chamber in close proximity tothe grain 19. The insulating sleeves 78 support the wire 71 which passestherethrough out of the chamber 13 to a battery S3 and a switch 84.

In operation, the switch 84 is closed permitting current, from thebattery 83, to flow through the high resistance wire 71 which heats upto raise the temperature of the grain 19. When the decompositiontemperature of the grain is reached the evolution of oxygen commencesand the fuel control valve 82 is turned on to inject fuel into thechamber 13 where reaction with the evolved oxygen takes place. When theheatreleased by the reaction of fuel and oxygen becomes sufcient tomaintain the grain 19 at its decomposition temperature, the switch 84 isopened to arrest the fiow of current through the high resistance wire71. The high temperature, high pressure combustion gases produced by thefuel-oxygen reaction discharge at high velocity and momentum through theexhaust nozzle 14 to impart a forward thrust to the unit.

The thrust of the unit may be regulated by adjusting the fuel controlvalve 82 or eliminated entirely by turning off said valve. Combustion offuel may be reinitiated and extinguished as desired by following theforegoing procedure.

What is claimed is: V i 1. A propulsion unit, comprising, a combustionchamber, a solid body of oxidizing material Within said .f

chamber, and meansfor injecting uid fuel into said chamber.

, 2. Apropulsion unit, comprising, a combustion chamber, anexhaustnozzle connected to said chamber, a Solid body of oxidizingmaterial within said chamber, means for injecting fluid fuel into saidchamber, means for controlling the rate of fuel injection, and ignitionmeans for initiating the combustion of said fuel within said chamber.

3. A propulsion unit, comprising, a combustion chamber, a solid body ofoxidizing material within said cham'- ber, a fuel injectorforintroducing fluid fuel into said chamber, and a plurality vof. injectorsfor initially introducing oxidizing gas into said chamber to initiateVcombustion of said fuel.

4. A propulsion unit, comprising, a combustion cham-Y. ber, a solid bodyof oxidizing material within said chamber, means for injecting fluidfuel into said chamber, and a flare forv preheating said oxidizingmaterial to decom# position temperature, whereupon 'oxygen isevolved'to` support the combustion of said fuel. Y

5. A propulsion unit, comprising, a combustion chamber, a solid body ofoxidizing material within said chamber, means for injecting liuid fuelinto said chamber, a

high resistance Vwire within saidV chamber, and a source of electricenergy associated with said wire for preheating lsaid oxidizing materialto decomposition temperature;L

whereupon oxygen is evolved to support the combustion of said fuel. Y

V6. A method of producing a propelling gaseous fluid which comprisessupplying a stream of iuid fuel'to the f surface of a'solid body of anoxidizing material.

7. A'rnethod as delined in claim 6 whereinv the oxidiz-X ing materialconsists essentially of a major proportion o f` an oxidizer and acatalyst to promote the decomposition" of said oxidizer. Y n

8. A method as defined in claim 7 wherein the solid body of oxidizingmaterial includes a binder toV consolidate said'oxidizer and saidcatalyst.

1li. Amethod as defined inA claimf 6 wherein the solid body'ofoxidizingmaterial consists essentially of a major, proportion of`potassium perchlorate and aminor'proporf. Y

tionfof manganese dioxide. Y V

Cil

12. A method as defined` in claim-6 wherein the solid 'Y body ofoxidizingI material consists essentially of a,y major proportion ofpotassium perchlorate, aminor proportion -K ofmanganese dioxide and a`binder consisting of .an eutectic mixture Y' of potassium( perchlorateand sodium `nitrate.'` 'Y Y 1,3. A method as aanedrn vclaim 6 whereinthe,solid Vbody ofY oxidizing materialconsisrts essentially of a majorproporton'of potassium-perchlorate, a minor proportion Y of manganesedioxide and a `binder consisting of an eutectic 'mixturejof sodiumnitrite andV potassium nitrate. 14. A method as defined in claim 6wherein the fuel is an organicfuel.

15. A method as dened in yclaim l6 whereinthe fuel 'i Y' l isfanvinorganiclfuel. v'

u 16. A method ,ofproducing a .propelling gaseous fluid which comprisessupplying'heat to the surface of a solid body of oxidizing V.material.until decomposition ofthe oxidizing' material4 is initiatedand'thereafter supplying 9. A method as. defined in `claim 6 wherein the.solid body'of oxidizing material consistsessentially ofa majorproportion of potassium perchlorate. l,

10. A method las defined in claim 9 wherein the solid body of oxidizingmaterial includes an oxidizer'selectedV from thergroup consisting ofammonium perchlorate andA ammonium nitrate.

a stream of fluid fuel to said surface. Y

v i References Citedfin the Yfiile of this patent `Y UNITED STATESPATENTS `24,898 y OTHER REFERENCES j i Mellor: Comprehensive Treatise onInorg. and Theo.-

retical Chem., Longmans, Green & Co., N.Y.'(1928), vol.' 8, pp. 317-318incl. V Y. Y Y Chemical .and Engineering News, vol; 23, No'. 17, Sep'- Ytember 1.0 1945, p. 1519.

1. A PROPULSION UNIT, COMPRISING, A COMBUSTION CHAMBER, A SOLID BODY OFOXIDIZING MATERIAL WITHIN SAID CHAMBER, AND MEANS FOR INJECTING FLUIDFUEL INTO SAID CHAMBER.
 6. A METHOD OF PRODUCING A PROPELLING GASEOUSXXXX WHICH COMPRISES SUPPLYING A STREAM OF FLUID FUEL TO THE SURFACE OFA SOLID BODY OF AN OXIDIZING MATERIAL.